Dr. Maximilian Ulbrich

Dr. Maximilian Ulbrich

Research in the Ulbrich Lab is focused on deciphering composition and dynamics of membrane proteins using novel single molecule techniques in living cells. In particular, we are curious how extracellular cues are processed by receptors in the cell membrane to trigger an intracellular signaling cascade. Examples are GPCR signaling or activation of immune cells.

We use fluorescent proteins or organic dyes to label the proteins of interest, and express them in Xenopus oocytes or mammalian cell lines. Single fluorescent proteins can be spatially resolved when the expression density is low enough, and it then becomes possible to count individual molecules or track their movement in the membrane. Co-localization of fluorescent tags of different colors can indicate the interaction of different proteins.

Currently we are investigating the role of G protein-coupled receptor oligomerization and their interactions with downstream signaling proteins. Although many GPCRs are shown to function well as monomers, a tendency to form dimers was reported frequently. However, the physiological role for dimerization is still unclear for most GPCRs. On the other hand, some GPCRs can only function as dimers because different functional units are distributed between the two subunits. One open question we want to solve is if a shift of the monomer-dimer equilibrium plays a role during signaling.

Another topic we are interested in is the association of synaptic glutamate receptors with auxiliary subunits. Nerve cells regulate the composition of glutamate receptors depending on the cell type and its activity. Many other proteins interact with the glutamate receptor to modulate its function and regulate trafficking to the synapse. We are trying to determine how many auxiliary subunits are associated with the glutamate receptor, to understand the stability of these interactions and if they compete for common binding sites.